A New Index for Comparing the Diversity of Population Inflows and Population Stocks

The paper introduces a new “diversification index” (DIV), which compares the composition of the current or recent population inflow and the composition of pre-existing population stock, with positive (negative) values signifying a process generating more (less) diversity in the stock. Higher absolute values for DIV signify larger differences in the composition of the inflows and the pre-existing stocks of population. DIV is easy to compute and interpret, adaptable to handle population inflows or outflows, and widely applicable to a variety of phenomena. The paper defines DIV, discusses its properties, and calculates it for several hypothetical cases as a way of showing its intuitive appeal, such as how it would reflect a neighborhood gentrification scenario. DIV indices for both race and income groupings are computed from 1992 to 2006 for three neighborhoods in Chicago to demonstrate how inter-temporal trends in DIV provide insights into neighborhood dynamics. Finally, the paper discusses extensions, potential weaknesses, and other caveats related to the use of DIV in future applied research

Can Small Incentives Have Large Effects? The Impact of Taxes versus Bonuses on Disposable Bag Use

Financial incentives are an important policy tool for encouraging prosocial behavior. However, evidence on the effect of very small financial incentives is mixed. Drawing on an original data set, I investigate the effect of a five-cent shopping bag tax imposed in the Washington Metropolitan Area. Despite the small size of the incentive, I find that the tax decreased the fraction of customers using a disposable bag by a substantial amount. In contrast, a similar policy that offered customers a five-cent bonus for reusable bag use generated virtually no effect on behavior. This pattern is consistent with a model of loss aversion and underscores the importance of the form a financial incentive takes - a tax versus a bonus - when designing policies aimed at shaping consumer behavior